In the gardening field, both at professional and amateur level, cutting heads are used to cut vegetation. These heads are coupled to the rotary shaft of a bush cutter that can be actuated by an endothermic or electric engine. The cutting heads have different members to cut vegetation. In many cases, the cutting member is a plastic line with a suitable cross-section, for instance a circular cross-section. A length of cutting line is accumulated on a spool in form of turns wound around an axial body of the spool, preferably between two flanges of the spool. The two opposite ends of the cutting line project through suitable holes for the passage of the cutting line provided, for instance, in bushings arranged on the perimeter wall of a housing inside which the spool is housed.
In use, the grass cutting head is quickly rotated around the rotation axis thereof and the line portions projecting from the housing of the spool are tensioned due to the centrifugal effect and act on the vegetation, cutting it.
The line portions projecting from the housing of the grass cutting head are subject to wear and breakage, such that it is periodically necessary to supply new portions of cutting line from the inside of the grass cutting head, by rotating the spool with respect to the housing inside which it is contained. Once the length of cutting line inside the grass cutting head is finished, it is necessary to load a new cutting line in the grass cutting head. To this end, the grass cutting head is usually opened, the spool housing being comprised of two separable portions. The spool is removed from the housing and turns of cutting line are wound around it, thus forming a new length. The opposite ends of the cutting line project from the spool and are then guided through passage holes provided in the housing perimeter wall, before closing the housing with the spool housed therein. These operations are long-lasting and onerous.
Therefore, grass cutting heads have been developed, wherein the cutting line replacement, i.e. the formation of a new length inside the housing and around the spool, is done without opening the housing. To this end, grass cutting heads are usually provided, wherein the spool has a through diameter hole, through which the cutting line is inserted, guided through the two opposite passage holes provided in the housing. To perform this operation, it is necessary to align the diametrically opposite through holes provided in the spool body with the cutting line passage holes provided in the housing containing the spool. It is also necessary that the central part of the spool is empty, to allow the line to pass there through. It is often necessary to use a guiding element, for instance a tube, which is made pass through the grass cutting head to guide the cutting line; otherwise, the cutting line could not enter all the mutually aligned openings to pass through the grass cutting head.
If the spool is not empty inside, and for instance the axial space is occupied by the hub of the bush cutter or other mechanical members, inside the spool axial body a curved guiding channel is provided, through which the free end of the cutting line is made to pass so as to guide it through the grass cutting head. This operation is complex and requires spools having a complex shape, which are difficult to mold and which must be often manufactured by assembling pieces made of plastic or other material, which have been previously molded separately.
The above mentioned solutions are not satisfactory. There is therefore a need to provide grass cutting heads that partly or entirely overcome or alleviate one or more of the drawbacks of the prior art grass cutting heads, and that especially make the replacement of a cutting line length easier.